        
        //计算rem
        (function (doc, win, undefined) {
            var docEl = doc.documentElement,
                resizeEvt = 'orientationchange' in win ? 'orientationchange' : 'resize',
                recalc = function () {
                    var clientWidth = document.body.clientWidth;
                    if (clientWidth === undefined) return;
                    docEl.style.fontSize = 20 * (clientWidth / 375) + 'px';
                };
            if (doc.addEventListener === undefined) return;
            win.addEventListener(resizeEvt, recalc, false);
            doc.addEventListener('DOMContentLoaded', recalc, false)
        })(document, window);